1. Field of the Invention
The present invention relates to a purge nozzle unit for purging a purge container having a purge space, a purge apparatus including the purge nozzle unit, and a load port.
2. Description of the Related Art
In a semiconductor manufacturing process, wafers are processed in a clean room for improved yield and quality. Instead of increasing the cleanliness of the entire interior of such a clean room, a system that incorporates “mini-environment system,” which locally increases the cleanliness only around wafers, has been adopted recently for transporting and otherwise processing wafers. The mini-environment system includes two important elements: a storage container known as a Front-Opening Unified Pod (FOUP) for transporting and retaining a wafer in a highly clean environment; and a load port, which is an interfacing tool for allowing a FOUP to exchange a wafer with a semiconductor manufacturing apparatus and for passing/receiving a FOUP itself to/from a transport apparatus.
A predetermined gaseous atmosphere suitable for water processing and fabrication is maintained in a semiconductor manufacturing apparatus. When a wafer is sent out from a FOUP into the semiconductor manufacturing apparatus, the internal space of the FOUP is communicate with that of the semiconductor manufacturing apparatus. Accordingly, if the environment is less clean in the FOUP than in the semiconductor manufacturing apparatus, air in the FOUP may enter the semiconductor manufacturing apparatus and adversely affect the gaseous atmosphere in the semiconductor manufacturing apparatus. Additionally, when the wafer is retrieved out of the semiconductor manufacturing apparatus into the FOUP, an oxide film may be formed on the surface of the wafer due to moisture, oxygen, or any other gas in a gaseous atmosphere in the FOUP.
As a technique for coping with the above-described problems, Japanese Patent Laid-Open No. 2009-038074 discloses a load port including a purge apparatus that opens a lid of a FOUP at a door section of the load port and blows a predetermined gas (e.g., nitrogen or inert gas) into the FOUP by a purge section (purge nozzle) provided on the semiconductor manufacturing apparatus side while internal spaces of the FOUP and the semiconductor manufacturing apparatus communicate with each other.
However, the purge apparatus using a so-called front purge system, which injects a predetermined gas from the front (the semiconductor manufacturing apparatus side) into a FOUP opened to the internal space of the semiconductor manufacturing apparatus through a carrying-in/carrying-out port and replaces the atmosphere in the FOUP with the predetermined gas, suffers from a disadvantage. The problem is that since the purging is performed while an opening of the FOUP is left open, and the internal space of the FOUP is in direct communication with the entire internal space of the semiconductor manufacturing apparatus, it is difficult to keep high concentration of the predetermined gas in the atmosphere in a FOUP, resulting in a lower maximum concentration of the predetermined gaseous atmosphere.
Japanese Patent Laid-Open No. 2011-187539 discloses a load port including a purge apparatus that injects a predetermined gas (e.g., nitrogen or inert gas) into a FOUP loaded with wafers placed on a table of the load port from the bottom to fill the FOUP and replace the atmosphere in the FOUP with the predetermined gas. The purge apparatus using a so-called bottom purge system, which injects gas such as nitrogen or dry air from the bottom of a FOUP into the FOUP and replaces the atmosphere in the FOUP with the predetermined gas, has an advantage over a purge apparatus using the front purge system in that a higher maximum concentration of the predetermined gaseous atmosphere can be reached.
Assume a case of a bottom purge system that has a purge nozzle always protruding upward from the top of table. In this case, when a FOUP is placed on the table, the purge nozzle is likely to hit against or be caught on a part of the FOUP before the FOUP is positioned by a positioning pin on the table, which may lead to a failure of the FOUP to be placed at an intended position.
A FOUP is often placed from above a load port onto the table by a transport apparatus such as an OHT (Overhead Hoist Transfer). A swing of the FOUP at the time of transport and placement is likely to cause the above-described problem. In addition, an injector (purge port) made of a resin provided on a bottom of the FOUP and brought into (close) contact with the purge nozzle at the time of purging may rub against the purge nozzle and wear at the time of placement of the FOUP on the table prior to purging.
For this reason, Japanese Patent Laid-Open No. 2011-187539 discloses a purge apparatus including a drive unit that moves a nozzle so as to contact with a purge port formed in a bottom of a FOUP while a positioning pin on a table is engaged with a positioning groove provided on the bottom of the FOUP.
As a specific example of the drive unit, Japanese Patent Laid-Open No. 2011-187539 discloses one that includes a pair of left and right air cylinders attached to opposite sides of a nozzle holder holding a nozzle and a common elevating plate whose opposite ends connected to working ends of the air cylinders and whose center is provided with the nozzle. The unit moves the nozzle up and down by driving the air cylinders in sync with each other to vertically move the elevating plate.
The example, however, involves air cylinders attached to opposite sides of the nozzle holder, and at least the top view dimensions of the nozzle holder increases by an amount corresponding to the air cylinders, which leads to the difficulty in size reduction.
Additionally, if such a pair of left and right air cylinders are not in sync with each other, an up-and-down action of the elevating plate and vertical movement of the nozzle holder and the nozzle itself associated with the up-and-down action of the elevating plate may become unstable or impossible.
Note that the above-described problems are not specific to a purge apparatus of a load port and may occur in a purge apparatus of something other than a load port, such as that of a storage or of a purge station.